Assessment of measurement performance for a low field side IDTT plasma position reflectometry system

Silva, F da; Ferreira, J.; Santos, J.; Heuraux, S.; Ricardo, E.; Tudisco, O.; Cavazzana, R.; D'Arcangelo, O.

doi:10.1016/j.fusengdes.2021.112405

Cited by 8 publications

(7 citation statements)

References 19 publications

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“…To predict the behaviour and capabilities of the proposed reflectometry system for DTT, three synthetic diagnostics (SD) were prepared. These SDs correspond to three O-mode reflectometers located on the LFS, with one on the midplane and two others located away from the midplane [43]. The simulations were performed using the 2D FDTD full-wave code REFMULF in two plasma scenarios envisioned for DTT, namely the 5 MA single null (SN) and double null (DN) configurations during the start-of-flat (SOF) phase of the discharge.…”

Section: Plasma Position and Shape Reflectometry In Dtt-a Test Bed Fo...mentioning

confidence: 99%

Advances, Challenges, and Future Perspectives of Microwave Reflectometry for Plasma Position and Shape Control on Future Nuclear Fusion Devices

Gonçalves

Varela

Silva

et al. 2023

Sensors

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Providing energy from fusion and finding ways to scale up the fusion process to commercial proportions in an efficient, economical, and environmentally benign way is one of the grand challenges for engineering. Controlling the burning plasma in real-time is one of the critical issues that need to be addressed. Plasma Position Reflectometry (PPR) is expected to have an important role in next-generation fusion machines, such as DEMO, as a diagnostic to monitor the position and shape of the plasma continuously, complementing magnetic diagnostics. The reflectometry diagnostic uses radar science methods in the microwave and millimetre wave frequency ranges and is envisaged to measure the radial edge density profile at several poloidal angles providing data for the feedback control of the plasma position and shape. While significant steps have already been given to accomplish that goal, with proof of concept tested first in ASDEX-Upgrade and afterward in COMPASS, important, ground-breaking work is still ongoing. The Divertor Test Tokamak (DTT) facility presents itself as the appropriate future fusion device to implement, develop, and test a PPR system, thus contributing to building a knowledge database in plasma position reflectometry required for its application in DEMO. At DEMO, the PPR diagnostic’s in-vessel antennas and waveguides, as well as the magnetic diagnostics, may be exposed to neutron irradiation fluences 5 to 50 times greater than those experienced by ITER. In the event of failure of either the magnetic or microwave diagnostics, the equilibrium control of the DEMO plasma may be jeopardized. It is, therefore, imperative to ensure that these systems are designed in such a way that they can be replaced if necessary. To perform reflectometry measurements at the 16 envisaged poloidal locations in DEMO, plasma-facing antennas and waveguides are needed to route the microwaves between the plasma through the DEMO upper ports (UPs) to the diagnostic hall. The main integration approach for this diagnostic is to incorporate these groups of antennas and waveguides into a diagnostics slim cassette (DSC), which is a dedicated complete poloidal segment specifically designed to be integrated with the water-cooled lithium lead (WCLL) breeding blanket system. This contribution presents the multiple engineering and physics challenges addressed while designing reflectometry diagnostics using radio science techniques. Namely, short-range dedicated radars for plasma position and shape control in future fusion experiments, the advances enabled by the designs for ITER and DEMO, and the future perspectives. One key development is in electronics, aiming at an advanced compact coherent fast frequency sweeping RF back-end [23–100 GHz in few μs] that is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). The compactness of this back-end design is crucial for the successful integration of many measurement channels in the reduced space available in future fusion machines. Prototype tests of these devices are foreseen to be performed in current nuclear fusion machines.

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Section: Plasma Position and Shape Reflectometry In Dtt-a Test Bed Fo...mentioning

confidence: 99%

Advances, Challenges, and Future Perspectives of Microwave Reflectometry for Plasma Position and Shape Control on Future Nuclear Fusion Devices

Gonçalves

Varela

Silva

et al. 2023

Sensors

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show abstract

“…For the last one we used a model based on the density profiles appearing in [3] using a fit on the extracted data based on the expression proposed in [4]. The full process to obtain the 2D poloidal maps, n e (x, y), is presented in [2]. For 3D density volume, n e (x, y, z), the 2 density map is extruded in the third dimension slab-wise, which is justified with the knowledge that the probing size in the toroidal direction (z) is much smaller than the major radius of the machine.…”

Section: Modelling and Simulation Setupmentioning

confidence: 99%

“…For 3D density volume, n e (x, y, z), the 2 density map is extruded in the third dimension slab-wise, which is justified with the knowledge that the probing size in the toroidal direction (z) is much smaller than the major radius of the machine. In [2] we conducted a study spanning the K, Ka, Q, V and W microwave bands, needed to probe until the separatrices of IDTT Single Null (SN) and double null scenarios. In this first 3D simulations, an ongoing work, we start with just bands K and Ka with the SN scenario, at the Start of Flattop (SOF), of the plasma current, at T = 36 s where a PPR is required to fulfil its main function.…”

Section: Modelling and Simulation Setupmentioning

confidence: 99%

“…A first effort has been performed using pyramidal horn antenna on a monostatic and two bistatic setups with a slab plasma [1]. This work follows that and proposes an analysis of one of the tentative reflectometers for a plasma position reflectometer for IDTT, as modelled in [2], confronting a 2D and 3D SDs for the equatorial position. We used the REFMULF, 2D, and REFMUL3, 3D, codes in this work.…”

Section: Introductionmentioning

confidence: 99%

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Benchmarking 2D against 3D FDTD codes for the assessment of the measurement performance of a low field side plasma position reflectometer applicable to IDTT

Silva¹,

Ricardo²,

Ferreira³

et al. 2022

J. Inst.

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O-mode reflectometry, a technique to diagnose fusion plasmas, is foreseen as a source of real-time (RT) plasma position and shape measurements for control purposes in the coming generation of machines such as DEMO. It is, thus, of paramount importance to predict the behavior and capabilities of these new reflectometry systems using synthetic diagnostics. Finite-difference time-domain (FDTD) time-dependent codes allow for a comprehensive description of reflectometry but are computationally demanding, especially when it comes to three-dimensional (3D) simulations, which requires access to High Performance Computing (HPC) facilities, making the use of two-dimensional (2D) codes much more common. It is important to understand the compromises made when using a 2D model in order to decide if it is applicable or if a 3D approach is required. This work attempts to answer this question by comparing simulations of a potential plasma position reflectometer (PPR) at the Low Field-Side (LFS) on the Italian Divertor Tokamak Test facility (IDTT) carried out using two full-wave FDTD codes, REFMULF (2D) and REFMUL3 (3D). In particular, the simulations consider one of IDTT’s foreseen plasma scenarios, namely, a Single Null (SN) configuration, at the Start Of Flat-top (SOF) of the plasma current.

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“…Microwave reflectometry was proposed [1] to supplement traditional magnetic diagnostics used for control on ITER 1 and was demonstrated on ASDEX Upgrade [2] as a potential replacement capable diagnostic for feedback position control. This control scheme is now under active design as a primary source for control position and shape measurements in DEMO [3,4] and to be further tested in future devices such as IDTT [5]. Using this diagnostic technique for control purposes involves distributing poloidally a large set of reflectometers, 2 probing the plasma in various radial Lines of Sight (LOS).…”

Section: Introductionmentioning

confidence: 99%

A 3D CAD model input pipeline for REFMUL3 full-wave FDTD 3D simulator

Santos¹,

Ricardo²,

Silva³

et al. 2021

J. Inst.

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The use of advanced simulation has become increasingly more important in the planning, design, and assessment phases of future fusion plasma diagnostics, and in the interpretation of experimental data from existing ones. The design cycle of complex reflectometry systems, such as the ones being planned for next generation machines (IDTT and DEMO), relies heavily on the results produced by synthetic diagnostics, used for system performance evaluation and prediction, both crucial in the design process decision making. These synthetic diagnostics need realistic representations of all system components to incorporate the main effects that shape their behavior. Some of the most important elements that are required to be well modelled and integrated in simulations are the wave launcher structures, such as the waveguides, tapers, and antennas, as well as the vessel wall structures and access to the plasma. The latter are of paramount importance and are often neglected in this type of studies. Faithfully modelling them is not an easy task, especially in 3D simulations. The procedure herein proposed consists in using CAD models of a given machine, together with parameterizable models of the launcher, to produce a description suited for Finite Difference Time Domain (FDTD) 3D simulation, combining the capabilities of real-world CAD design with the power of simulation. However, CAD model geometric descriptions are incompatible with the ones used by standard FDTD codes. CAD software usually outputs models in a tessellated mesh while FDTD simulators use Volumetric Pixel (VOXEL) descriptions. To solve this interface problem, we implemented a pipeline to automatically convert complex CAD models of tokamak vessel components and wave launcher structures to the VOXEL input required by REFMUL3, a full wave 3D Maxwell FDTD parallel code. To illustrate the full procedure, a complex reflectometry synthetic diagnostic for IDTT was setup, converted and simulated. This setup includes 3 antennas recessed into the vessel wall, for thermal protection, one for transmission and reception, and two just for reception.

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Assessment of measurement performance for a low field side IDTT plasma position reflectometry system

Cited by 8 publications

References 19 publications

Advances, Challenges, and Future Perspectives of Microwave Reflectometry for Plasma Position and Shape Control on Future Nuclear Fusion Devices

Advances, Challenges, and Future Perspectives of Microwave Reflectometry for Plasma Position and Shape Control on Future Nuclear Fusion Devices

Benchmarking 2D against 3D FDTD codes for the assessment of the measurement performance of a low field side plasma position reflectometer applicable to IDTT

A 3D CAD model input pipeline for REFMUL3 full-wave FDTD 3D simulator

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